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QUICK: NAME a famous automaker who first manufactured aero engines.
Oh, the one with the spinning prop logo?
Actually, I was thinking of an even earlier one: W.O. Bentley and his B.R.1 rotary aero engine.
In 1912, W.O. (Walter Owen) and his brother H.M. (Horace Millner) established Bentley and Bentley to import French DPF cars into England. Later, during World War I, as a Lieutenant in the Royal Navy Air Service, W.O. accepted a challenge from the Admiralty to solve an aero engineering problem: The British were licensing production of the French Clerget 9B aero rotary, which powered, among other aircraft, the Sopwith Camel.
The Clerget 9B was a nine-cylinder rotary displacing 16.3 liters and producing 130 hp at 1250 rpm—and, as a rotary, this meant the entire engine, except for its fixed crankshaft, revved at this speed! The 9B weighed 381 lb., working out to 0.34 hp/lb., had a cost of £907 each, and tended to overheat.
Could W.O. beat the Clerget with a design of his own?
W.O.’s approach was both classic (he added displacement) as well as advanced (he swapped the Clerget’s cast-iron cylinders for aluminum ones fitted with pressed-in steel liners).
The B.R.1 paid homage to the Clerget in many ways: It too was a nine-cylinder powerplant relying on air cooling as its cylinders rotated at 1250 rpm. However, the B.R.1 produced 150 hp from its 17.3 liters, weighed only 16 lb. more than the Clerget’s 381 lb.—and cost £605 each.
Jane’s reported that the B.R.1 produced 0.38 hp/lb., versus the Clerget’s 0.34. W.O.’s design consumed fuel at a rate of 11.0 Imperial gallons/hour, compared with the Clerget 9B’s 12.0/hour.
Also, suggesting why WWI pilots never suffered constipation, both engines burned through about 12 Imperial pints/hour of lubricant, typically castor oil.
The B.R.1 became standardized for Sopwith Camels in the Royal Navy Air Service, though Bentley never achieved production capacity equal to demand, and most Royal Air Force Camels continued using the inferior, more expensive Clerget.
W.O.’s B.R.1 evolved into the B.R.2, displacing 24.9 liters, weighing 475 lb., by 1918 producing 250 hp (0.53 hp/lb.), and the last rotary engine used by the RAF. Later aero engines of this cylinder appearance were radials, not rotaries.
With war’s end, in 1919 W.O. and H.M. committed to the automobile in establishing Bentley Motors Limited. Before long, W.O. would again show the French what for. This time, his designs would dominate 24-hour endurance racing in a place called Le Mans. ds
© Dennis Simanaitis, SimanaitisSays, 2017